The present invention generally relates to a method and a device for controlling a drive system, in particular a hydraulic traveling drive of a crane, a caterpillar, an industrial truck or a construction machine, which has at least one drive unit for an element to be driven. On the one hand, the invention relates to a method, in which a desired value of an output parameter as well as a power limit value for the at least one drive unit are specified and in dependence on the specified desired value of the output parameter and the specified power limit value at least one actuating signal is provided for the at least one drive unit. The invention in particular relates to a method, in which at least two separate drive units are provided for a left drive wheel and a right drive wheel, wherein one desired speed each is specified for the two wheels and in dependence on the specified desired speeds at least one actuating signal is provided for the drive units. Furthermore, the invention relates to a control device for controlling such drive system, comprising a control signal circuit for providing an actuating signal for adjusting the at least one drive unit in dependence on a specified desired value of an output parameter and a specified power limit value for the at least one drive unit. Finally, the invention relates to a crane, a caterpillar or a construction machine with such a control device.
Cranes, but also other construction machines, regularly have hydraulic drive systems with at least one closed hydraulic circuit, which has a hydraulic pump in combination with a hydraulic motor. By means of such hydraulic drive systems, various drive functions are realized for instance on cranes, and in particular hoisting winch drives, chain drives or wheel drives can be realized in this way. The  hydraulic pump regularly is driven via a drive unit, such as an internal combustion engine. The hydraulic stream generated by the pump is translated into the corresponding actuating movement by the hydraulic motor coupled therewith. In order to control the corresponding actuating movement in a precise and stable way, the speed of the hydraulic motor must be controlled accordingly, the delivery rate of the hydraulic pump and the absorption volume of the hydraulic motor being adjustable, for instance by using adjustable swash plate designs of these components, but other designs are possible as well. On the one hand, a fast response of the system should be achieved with corresponding operating or control commands. On the other hand, operating the actuators too fast or overriding the same can lead to instabilities of the drive system.
Construction machines such as cranes, caterpillars and the like, which can have a wheel drive or also a chain drive, regularly are moved on grounds such as gravel tracks, loamy or gravelly grounds or generally soil without surface coating, which often involve an only insufficient traction. This involves the corresponding traction problems during acceleration and braking. To remedy these problems, differential locks frequently are used, which force the drive wheels or chains of the left track to be coupled mechanically with the drive wheels of the left track. However, this in turn involves problems during cornering, in particular on grounds with higher traction. The slip induced by differential locks leads to premature wear both of the driveable pavement and of the corresponding drive elements.